Rotary drives are known, in which the transmission means, e.g. a rigid shaft, a chord or the like twists, or e.g. in the case of belts, chains, bands and the like is stretched by tensile forces. Each of these drive types has its own intrinsic advantages and disadvantages with respect to the drive transmission and these are also known. The rigid shaft is mainly suitable for force transmission over longer distances and it must be borne in mind that in the case of considerable loading, there can be a disturbing twisting effect. Chords in the sense of flexible shafts or chains are used for transmission over shorter distances. When using e.g. chain, a "rigid" transmission is expected and when using chords a flexible transmission, the latter only being suitable for the transmission of small torques due to the high torsion angle on loading.
For example, U.S. Pat. No. 3,718,051 discloses a force transmission system, which transmits rotary movement between a drive and a power take-off by means of flexible chain guides. The transmission means is constituted by a plurality of unconnected balls, which are pushed through the chain channels. In order to obtain a relatively uniform force or power transmission, the chain guide in the pushing drum must be very rigid, because if it had, flexible walls, the balls, the rounded surfaces of which are in contact with one another are positionally unstable in the pushing operation and must be positioned and stabilized by the channel walls. However, in the pulling drum, in which during the "return" of the balls substantially no forces act and certainly no forces resulting from force transmission to the balls, the elasticity or rather the stability of the chain guide is of minor significance. Thus, very narrow limits are applied to the flexibility of the described force transmission by means of balls. A uniform force transmission is not readily possible in the flexible construction.